JP2018026372A - Polishing liquid for CMP and polishing method using the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a polishing liquid for CMP capable of protecting a cobalt layer by suppressing etching speed of the cobalt layer to 10 nm/min or less while maintaining excellent polishing speed with respect to the cobalt layer, and also to provide a polishing method using the polishing liquid for CMP.SOLUTION: Disclosed is a polishing liquid for CMP which is used for polishing of a surface to be polished having at least a cobalt containing part, and a metal containing part containing metal except cobalt. The polishing liquid for CMP contains two types of metal corrosion inhibitors, abrasive particles and water and pH thereof is 4.0 or less. Each of two types of metal corrosion inhibitors is azoles (excluding inorganic acid salt).SELECTED DRAWING: Figure 1

Description

  The present invention relates to a polishing liquid for CMP and a polishing method using the same.

  2. Description of the Related Art In recent years, new microfabrication techniques have been developed along with higher integration and higher performance of semiconductor large-scale integrated circuits (Large-Scale Integration; hereinafter referred to as “LSI”). A chemical mechanical polishing (hereinafter referred to as “CMP”) method is one of them. The CMP method is a technique frequently used in planarization of an insulating material part, formation of a metal plug, formation of a buried wiring, etc. in an LSI manufacturing process, particularly in a multilayer wiring forming process.

  In recent years, a so-called damascene method has been adopted for the formation of embedded wiring. In the damascene method, a conductive material portion is deposited on an insulating material portion having a concave portion (for example, a groove portion) and a convex portion (for example, a raised portion) formed in advance on the surface, and the conductive material is embedded in the concave portion. Next, the conductive material deposited on the convex portion (that is, the conductive material other than in the concave portion) is removed by CMP to form a buried wiring.

  In the CMP of the conductive material portion, for example, first, a polishing pad is attached on a circular polishing platen (platen), and the surface of the polishing pad is immersed in a CMP polishing liquid. Next, the surface on which the conductive material portion of the substrate is formed is pressed against the polishing pad, and a predetermined pressure (hereinafter referred to as “polishing pressure”) is applied from the back surface of the substrate. Thereafter, the polishing surface plate is rotated in this state, and the conductive material on the convex portion is removed by mechanical friction between the polishing liquid for CMP and the conductive material portion.

  On the other hand, as shown in FIG. 3A, a barrier metal portion 2 is usually provided between the insulating material portion 1 having irregularities and the conductive material portion 3 provided on the insulating material portion 1. It is formed. The purpose of providing the barrier metal portion 2 is to prevent the conductive material from diffusing into the insulating material portion 1 and to improve the adhesion between the insulating material portion 1 and the conductive material portion 3. The barrier metal portion 2 is formed of a barrier metal (hereinafter sometimes referred to as “barrier metal”). Since the barrier metal is a conductor, it is necessary to remove the barrier metal in the same manner as the conductive material except for the concave portion (that is, the wiring portion) in which the conductive material is embedded.

  These removals include a “first polishing step” in which the conductive material portion 3 is polished from the state shown in FIG. 3A to the state shown in FIG. 3B, and the state shown in FIG. In general, a two-stage polishing method in which polishing is performed with different polishing liquids for CMP is applied to the “second polishing step” in which the barrier metal portion 2 is polished from the state shown in FIG. 3C to the state shown in FIG. Yes.

  By the way, with the miniaturization of the design rule, the thickness of each part tends to be reduced. However, the barrier metal part 2 becomes thin, and the effect of preventing the diffusion of the conductive material is reduced. In addition, the adhesion with the conductive material portion 3 tends to decrease. Furthermore, since the wiring width becomes narrower, it becomes difficult to embed the conductive material in the recess (that is, the embedding property is lowered), and voids called voids are easily generated in the conductive material portion 3. Challenges arise.

  For this reason, use of cobalt (Co) as a barrier metal has been studied. By using cobalt, diffusion of the conductive material can be suppressed. In addition, since cobalt has a high affinity with a conductive material (for example, a copper-based metal such as copper or a copper alloy), the embedding property of the conductive material is improved. Furthermore, the adhesion between the insulating material and the conductive substance can be supplemented.

  When cobalt is used for the barrier metal part 2, it is necessary to use a polishing slurry for CMP that can remove cobalt. Various types of CMP polishing liquid for metal are known, but on the other hand, when there is a certain CMP polishing liquid, it cannot always remove any metal. As conventional CMP polishing liquids for metals, those for which the object to be removed by polishing is a metal such as copper, tantalum, titanium, tungsten, and aluminum are known. However, there are few known polishing liquids for CMP that use cobalt as a polishing target, although several examples have been reported as in Patent Documents 1 to 3 below.

JP 2011-91248 A JP 2012-182158 A JP2013-42123A

  According to the knowledge of the present inventors, cobalt is more corrosive than metals such as copper-based metals that have been used as conductive materials. Cobalt is excessively etched or slits are formed in the wiring pattern. As a result, there is a concern that metal ions may diffuse into the insulating material portion without fulfilling the function as the barrier metal portion. When metal ions diffuse into the insulating material portion, there is a high possibility that a short circuit occurs in the semiconductor device. On the other hand, in order to prevent this, if a metal anticorrosive having a strong anticorrosive action is added to the CMP polishing liquid or the amount of the metal anticorrosive added is increased, the polishing rate of cobalt is lowered.

  The present invention is intended to solve the above-mentioned problems, and polishing for CMP capable of protecting the cobalt layer by suppressing the etching rate of the cobalt layer to 10 nm / min or less while maintaining a good polishing rate for the cobalt layer. It is an object of the present invention to provide a liquid and a polishing method using the CMP polishing liquid.

  As a result of intensive studies to solve such conventional problems, the present inventors have increased the etching rate of the cobalt layer while maintaining a good polishing rate for the cobalt layer by using a specific anticorrosive agent. It was found that the cobalt layer can be protected with effective suppression.

  That is, an embodiment of the present invention is a polishing slurry for CMP used for polishing a surface to be polished having at least a cobalt-containing portion and a metal-containing portion containing a metal other than cobalt, and two kinds of metal anticorrosives Further, the present invention relates to a polishing slurry for CMP, which contains abrasive particles and water, has a pH of 4.0 or less, and both of the two types of metal anticorrosives are azoles (excluding salts of inorganic acids).

  The CMP polishing liquid may further contain a water-soluble polymer. Thereby, it is possible to suppress galvanic corrosion of the cobalt-containing portion, protect the surface to be polished, reduce the occurrence of defects, and suppress corrosion.

  In one embodiment of the polishing liquid for CMP, the abrasive particles include at least one selected from the group consisting of silica particles, alumina particles, ceria particles, titania particles, zirconia particles, germania particles, and modified products thereof. But you can. Thereby, there exists a tendency for the grinding | polishing rate of the metal containing part provided in the vicinity of the cobalt containing part to improve.

  One embodiment of the polishing slurry for CMP may further contain a metal oxidizing agent. Thereby, the grinding | polishing speed | rate of a metal containing part can be improved more.

  The CMP polishing liquid may further include an organic solvent. Thereby, the wettability of the metal containing part provided in the vicinity of the cobalt containing part can be improved, and the polishing rate of the metal containing part can be further improved.

  In another embodiment of the present invention, at least one of the cobalt-containing portions of the surface to be polished having at least a cobalt-containing portion and a metal-containing portion containing a metal other than cobalt, using any of the CMP polishing liquids. The present invention relates to a polishing method in which a part is polished and removed.

  In another embodiment of the present invention, an insulating material portion having a concave portion and a convex portion on a surface, a barrier metal portion covering the insulating material portion along the concave portion and the convex portion, and filling the concave portion with the barrier A step of preparing a substrate having a conductive substance part covering the metal part, the barrier metal part having a cobalt-containing part, and the conductive substance part having a metal-containing part containing a metal other than cobalt, A first polishing step for polishing the conductive material portion to expose the barrier metal portion on the convex portion, and any one of the CMP polishing for the barrier metal portion exposed in the first polishing step It is related with the grinding | polishing method which has the 2nd grinding | polishing process removed by grind | polishing with a liquid.

  In one embodiment of the polishing method, the insulating material portion is a silicon-based insulator or an organic polymer-based insulator.

  In one embodiment of the polishing method, the conductive material portion contains copper as a main component.

  In one embodiment of the polishing method, the barrier metal part has a cobalt-containing part and at least one selected from the group consisting of a tantalum-containing part, a titanium-containing part, and a ruthenium-containing part.

  According to the embodiment of the present invention, the CMP polishing liquid capable of protecting the cobalt layer by suppressing the etching rate of the cobalt layer to 10 nm / min or less while maintaining a good polishing rate for the cobalt layer of the cobalt-containing portion, and the CMP A polishing method using a polishing slurry for the use can be provided.

It is a cross-sectional schematic diagram which shows an example of the grinding | polishing method which is embodiment of this invention. It is a cross-sectional schematic diagram which shows an example of the grinding | polishing method which is embodiment of this invention. It is a cross-sectional schematic diagram which shows the formation process of the embedded wiring by the conventional damascene method.

In the embodiment of the present invention, the “polishing rate” means a rate at which the substance A to be CMPed is removed by polishing (for example, a reduction amount of the thickness of the substance A per time. Removable Rate).
“Process” is not only an independent process, but even if it cannot be clearly distinguished from other processes, it cannot be clearly distinguished from other processes as long as the operations specified in the “process” are performed. A process is also included.
The numerical range indicated by using “to” indicates a range including the numerical values described before and after “to” as the minimum value and the maximum value, respectively.
The content of each component in the CMP polishing liquid is the sum of the plurality of substances present in the CMP polishing liquid unless there is a specific indication when there are a plurality of substances corresponding to each component in the CMP polishing liquid. Means quantity.

Hereinafter, embodiments of the present invention will be described in detail.
<CMP polishing liquid>
The CMP polishing liquid according to this embodiment is a CMP polishing liquid used for polishing a surface to be polished having at least a cobalt-containing portion and a metal-containing portion containing a metal other than cobalt. The polishing slurry for CMP according to this embodiment contains abrasive particles (hereinafter sometimes referred to as “abrasive grains”), two types of metal anticorrosives, and water, and has a pH of 4.0 or less.

<Abrasive>
The polishing liquid for CMP contains abrasive grains. Due to the inclusion of the abrasive grains, the polishing rate of the metal-containing part provided in the vicinity of the cobalt-containing part tends to be improved. An abrasive grain can be used individually by 1 type or in mixture of 2 or more types.

  As abrasive grains, inorganic abrasive particles such as silica particles, alumina particles, zirconia particles, ceria particles, titania particles, germania particles and silicon carbide particles; organic abrasive particles such as polystyrene particles, polyacrylic acid particles and polyvinyl chloride particles; These modified products are exemplified.

  The abrasive is preferably at least one selected from the group consisting of silica particles, alumina particles, zirconia particles, ceria particles, titania particles, germania particles, and modified products thereof.

  Silica particles and alumina particles are preferred from the viewpoint of good dispersion stability in the polishing liquid for CMP and a small number of polishing scratches (sometimes referred to as “scratches”) generated by CMP. Colloidal silica and colloidal alumina Is more preferable, and colloidal silica is more preferable.

  The content of the abrasive grains is preferably 1.0% by mass or more, more preferably 1.2% by mass or more, and further preferably 1.5% by mass in the total mass of the polishing slurry for CMP from the viewpoint of obtaining a good polishing rate. It is at least mass%. The content of the abrasive grains is preferably 5.0% by mass or less, more preferably 5.0% by mass or less, based on the total mass of the polishing slurry for CMP, from the viewpoint of maintaining good dispersion stability of the abrasive grains and suppressing the occurrence of polishing flaws. Is 4.5% by mass or less, more preferably 4.0% by mass or less.

  The average particle diameter of the abrasive grains is preferably 40 nm or more, more preferably 45 nm or more, and further preferably 50 nm or more from the viewpoint of obtaining a good polishing rate. The average particle size of the abrasive grains is preferably 90 nm or less, more preferably 85 nm or less, and still more preferably 80 nm or less, from the viewpoint of suppressing polishing flaws.

The particle diameter of the abrasive grains can be measured with a light diffraction scattering type particle size distribution meter (for example, “COULTER N4SD” manufactured by COULTER Electronics) using a water dispersion obtained by appropriately diluting a CMP polishing liquid with water as a sample. For example, the measurement conditions of the light diffraction / scattering particle size distribution meter are: measurement temperature 20 ° C., solvent refractive index 1.333 (corresponding to the refractive index of water), particle refractive index Unknown (setting), solvent viscosity 1.005 mPa (water Equivalent to viscosity), Run Time 200 sec, laser incident angle 90 °. If the intensity (scattering intensity, corresponding to turbidity) is higher than 4 × 10 ⁵ so that it falls within the range of 5 × 10 ⁴ to 4 × 10 ⁵ , the polishing slurry for CMP is diluted with water. After obtaining the dispersion, measurement is performed.

<Metal anticorrosive>
The CMP polishing liquid contains two types of metal anticorrosives. By containing two kinds of metal anticorrosives, the etching of cobalt can be suppressed to 10 nm / min or less while maintaining a good polishing rate with respect to the cobalt-containing portion.

  The metal anticorrosive is preferably selected from the group consisting of azoles from the viewpoint of suppressing etching of the cobalt-containing part while maintaining a good polishing rate for the cobalt-containing part.

  Specific examples of the azoles include pyrazole, 1-allyl-3,5-dimethylpyrazole, 3,5-di (2-pyridyl) pyrazole, 3,5-diisopropylpyrazole, 3,5-dimethyl-1- Hydroxymethylpyrazole, 3,5-dimethyl-1-phenylpyrazole, 3,5-dimethylpyrazole, 3-amino-5-hydroxypyrazole, 4-methylpyrazole, N-methylpyrazole, 3-aminopyrazole, 3-amino- Pyrazoles such as 5-methylpyrazole; 1,1′-carbonylbis-1H-imidazole, 1,1′-oxalyldiimidazole, 1,2,4,5-tetramethylimidazole, 1,2-dimethyl-5 Nitroimidazole, 1,2-dimethylimidazole, 1- (3-aminopropyl) imidazole, 1 -Imidazoles such as butylimidazole, 1-ethylimidazole, 1-methylimidazole, 1H-1,2,3-triazolo [4,5-b] pyridine; thiazoles such as 2,4-dimethylthiazole; 2-mercapto Benzothiazoles such as benzothiazole; tetrazoles such as tetrazole, 5-methyltetrazole, 5-aminotetrazole, 1,5-pentamethylenetetrazole, 1- (2-dimethylaminoethyl) -5-mercaptotetrazole; Triazoles such as 1,3-triazole, 1,2,4-triazole, 3-amino-1,2,4-triazole; benzotriazole, 1-hydroxybenzotriazole, 1- Dihydroxypropyl benzotriazol, 2,3-dicarboxypropyl benzotriazol , 4-hydroxybenzotriazole - le, 4-carboxy benzotriazolate - le, 5-methylbenzotriazole, benzotriazole such as 1- (formamide methyl)-1H-benzotriazole.

  It consists of pyrazoles, imidazoles, benzothiazoles, thiazoles, and tetrazoles as metal anticorrosives from the viewpoint of effectively suppressing etching of the cobalt-containing parts while maintaining a good polishing rate for the cobalt-containing parts. Preferably it is selected from the group. More preferably, it is selected from the group consisting of benzotriazoles.

  From the viewpoint of suppressing galvanic corrosion of the cobalt-containing part, the total content of the metal anticorrosive is preferably 0.001% by mass or more, more preferably 0.01% by mass or more, more preferably, in the total mass of the polishing slurry for CMP. Preferably it is 0.02 mass% or more. Further, the content of the metal anticorrosive is 5% by mass or less, more preferably 3% by mass or less, more preferably 1% by mass in the total mass of the polishing slurry for CMP from the viewpoint of obtaining a good polishing rate of the cobalt-containing part. % Or less.

<Organic acids>
The CMP polishing liquid may further contain organic acids. Organic acids have the effect of improving the polishing rate for the cobalt-containing part and the metal-containing part. Organic acids include organic acids, salts of organic acids, anhydrides of organic acids, and esters of organic acids. Among organic acids, phthalic acids are preferable from the viewpoint of suppressing corrosion of the cobalt-containing part. By using phthalic acids, a good polishing rate of the cobalt-containing part can be obtained, and corrosion can be suppressed. Phthalic acids include phthalic acid, salts of phthalic acid, phthalic anhydride, and esters of phthalic acid, which may or may not have a substituent.

  Examples of phthalic acids include alkylphthalic acids such as phthalic acid, 3-methylphthalic acid and 4-methylphthalic acid; aminophthalic acids such as 3-aminophthalic acid and 4-aminophthalic acid; nitrophthalic acids such as 3-nitrophthalic acid and 4-nitrophthalic acid These salts; their anhydrides; their esters and the like. Of these, phthalic acid (methylphthalic acid) having a methyl group as a substituent is preferable, 3-methylphthalic acid and 4-methylphthalic acid are more preferable, and 4-methylphthalic acid is still more preferable. Examples of the salt include salts with alkali metals such as sodium and potassium, salts with alkaline earth metals such as magnesium and calcium, ammonium salts and the like.

  In the case where the CMP polishing liquid contains organic acids, the content thereof is preferably 0.001% by mass or more, more preferably in the total mass of the CMP polishing liquid, from the viewpoint of suppressing galvanic corrosion of the cobalt-containing portion. It is 0.01 mass% or more, More preferably, it is 0.02 mass% or more. In addition, the content of the organic acids is 5% by mass or less, more preferably 3% by mass or less, and further preferably 1% by mass in the total mass of the polishing slurry for CMP from the viewpoint of obtaining a good polishing rate of the cobalt-containing part. It is as follows.

<Metal oxidizing agent>
The CMP polishing liquid preferably contains a metal oxidizing agent. The metal oxidizing agent is not particularly limited, and examples thereof include hydrogen peroxide, peroxosulfate, nitric acid, potassium periodate, hypochlorous acid, and ozone. From the viewpoint of improving the polishing rate of the metal-containing part, hydrogen peroxide is particularly preferable. A metal oxidizing agent can be used individually by 1 type or in mixture of 2 or more types.

  When the CMP polishing liquid contains a metal oxidizer, the content is preferably 0.01% by mass or more in the total mass of the CMP polishing liquid from the viewpoint of obtaining a good polishing rate of the cobalt-containing part. 0.02% by mass or more is preferable, and 0.05% by mass or more is more preferable. The content of the metal oxidant is preferably 30% by mass or less, more preferably 15% by mass or less, and still more preferably 10% by mass or less, from the viewpoint of preventing the polished surface from being rough.

<Organic solvent>
The CMP polishing liquid may further contain an organic solvent. By including the organic solvent, the wettability of the polishing slurry for CMP with respect to the metal-containing part provided in the vicinity of the cobalt-containing part can be improved. Although there is no restriction | limiting in particular as an organic solvent, What can mix with water is preferable and what melt | dissolves 0.1g or more with respect to 100g of water at 25 degreeC is more preferable. An organic solvent can be used individually by 1 type or in mixture of 2 or more types.

  Organic solvents include carbonates such as ethylene carbonate, propylene carbonate, dimethyl carbonate, diethyl carbonate, and methyl ethyl carbonate; lactones such as butyl lactone and propyl lactone; ethylene glycol, propylene glycol, diethylene glycol, dipropylene glycol, triethylene Glycols such as glycol and tripropylene glycol; ethers such as tetrahydrofuran, dioxane, dimethoxyethane, polyethylene oxide, ethylene glycol monomethyl acetate, diethylene glycol monoethyl ether acetate, propylene glycol monomethyl ether acetate (excluding glycol derivatives); methanol Ethanol, propanol, n-butanol, Alcohols (monoalcohols) such as pentanol, n-hexanol, isopropanol, 3-methoxy-3-methyl-1-butanol; ketones such as acetone and methyl ethyl ketone; amides such as dimethylformamide and n-methylpyrrolidone Esters such as ethyl acetate and ethyl lactate (excluding carbonates and lactones); sulfolanes such as sulfolane;

  The organic solvent may be a derivative of glycols. For example, ethylene glycol monomethyl ether, propylene glycol monomethyl ether, diethylene glycol monomethyl ether, dipropylene glycol monomethyl ether, triethylene glycol monomethyl ether, tripropylene glycol monomethyl ether, ethylene glycol monoethyl ether, propylene glycol monoethyl ether, diethylene glycol monoethyl ether , Dipropylene glycol monoethyl ether, triethylene glycol monoethyl ether, tripropylene glycol monoethyl ether, ethylene glycol monopropyl ether, propylene glycol monopropyl ether, diethylene glycol monopropyl ether, triethylene glycol monopropyl ether Glycol monoethers such as tripropylene glycol monopropyl ether, ethylene glycol monobutyl ether, propylene glycol monobutyl ether, diethylene glycol monobutyl ether, tripropylene glycol monobutyl ether, triethylene glycol monobutyl ether, tripropylene glycol monobutyl ether; ethylene glycol dimethyl ether, propylene Glycol dimethyl ether, diethylene glycol dimethyl ether, dipropylene glycol dimethyl ether, triethylene glycol dimethyl ethyl ether, tripropylene glycol dimethyl ether, ethylene glycol diethyl ether, propylene glycol diethyl ether, diethylene glycol diethyl Ether, dipropylene glycol diethyl ether, triethylene glycol diethyl ether, tripropylene glycol diethyl ether, ethylene glycol dipropyl ether, propylene glycol dipropyl ether, diethylene glycol dipropyl ether, dipropylene glycol dipropyl ether, triethylene glycol dipropyl ether And glycol ethers such as tripropylene glycol dipropyl ether, ethylene glycol dibutyl ether, propylene glycol dibutyl ether, diethylene glycol dibutyl ether, dipropylene glycol dibutyl ether, triethylene glycol dibutyl ether, and tripropylene glycol dibutyl ether.

  The organic solvent is preferably at least one selected from glycols, derivatives of glycols, alcohols, and carbonates, and more preferably alcohols.

  When the CMP polishing liquid contains an organic solvent, the content is preferably 0.1% by mass or more in the total mass of the CMP polishing liquid from the viewpoint of obtaining good wettability with respect to the metal-containing portion. 0.2 mass% or more is more preferable, and 0.5 mass% or more is still more preferable. Further, the content of the organic solvent is preferably 95% by mass or less and more preferably 50% by mass or less in the total mass of the polishing slurry for CMP from the viewpoint of preventing the possibility of ignition and safely implementing the manufacturing process. 10 mass% or less is further more preferable, 5 mass% or less is especially preferable, and 3 mass% or less is very preferable.

<Water-soluble polymer>
The CMP polishing liquid may further contain a water-soluble polymer. By containing the water-soluble polymer, it is possible to suppress galvanic corrosion of the cobalt-containing portion, protect the surface to be polished, reduce the occurrence of defects (defects), and the like. The water-soluble polymer is preferably one that dissolves at least 0.1 g per 100 g of water at 25 ° C. A water-soluble polymer can be used individually by 1 type or in mixture of 2 or more types.

The water-soluble polymer is preferably a water-soluble polymer having a carboxylic acid group or a carboxylic acid group. The polycarboxylic acid and a salt thereof (“a salt of a polycarboxylic acid” means “a part of a carboxylic acid group of a polycarboxylic acid or More preferably it means “polymers all substituted with carboxylic acid groups”). Examples of the carboxylate group include an ammonium carboxylate group and a sodium carboxylate group.
Examples of polycarboxylic acids and salts thereof include homopolymers of monomers having a carboxylic acid group such as acrylic acid, methacrylic acid, and maleic acid; polymers in which a part or all of the homopolymer is substituted with a carboxylic acid group; A copolymer of a monomer having a carboxylic acid group such as acrylic acid, methacrylic acid, and maleic acid and a carboxylic acid derivative such as an alkyl ester of carboxylic acid; a part or all of the copolymer is substituted with a carboxylic acid group And other copolymers. Specific examples include polyacrylic acid; polyacrylic acid ammonium salt (meaning “polymer in which a part or all of the carboxylic acid groups of polyacrylic acid are substituted with ammonium carboxylate”).

  Furthermore, examples of the water-soluble polymer include polycarboxylic acids other than the above such as polyaspartic acid, polyglutamic acid, polylysine, polymalic acid, polyamic acid, polyamic acid ammonium salt, polyamic acid sodium salt, polyglyoxylic acid, and salts thereof; Examples thereof include polysaccharides such as alginic acid, pectic acid, carboxymethylcellulose, agar, curdlan and pullulan; and vinyl polymers such as polyvinyl alcohol, polyvinylpyrrolidone and polyacrolein.

  Among water-soluble polymers, polycarboxylic acid or a salt thereof; pectic acid; agar; polymalic acid; polyacrylamide; polyvinyl alcohol; polyvinyl pyrrolidone; an ester or ammonium salt thereof is preferable, and a polyacrylic acid ammonium salt is more preferable.

  The weight average molecular weight of the water-soluble polymer is preferably 500 or more, more preferably 1,000 or more, still more preferably 2,000 or more, particularly preferably 5,000 or more, from the viewpoint of obtaining a high polishing rate of the cobalt-containing part. is there. Further, the weight average molecular weight of the water-soluble polymer is preferably 1,000,000 or less, more preferably 500,000 or less, still more preferably 200,000 or less, particularly preferably 100,000 or less, from the viewpoint of solubility. Most preferably, it is 20,000 or less.

  In the embodiment of the present invention, as a weight average molecular weight, a value measured by gel permeation chromatography (GPC) based on the following method and converted to standard polyacrylic acid can be used.

(conditions)
Detector: manufactured by Hitachi, Ltd., RI-monitor “L-3000”
Integrator: Hitachi, Ltd., GPC integrator “D-2200”
Pump: “L-6000” manufactured by Hitachi, Ltd.
Degassing device: “Shodex DEGAS” manufactured by Showa Denko KK
Column: “GL-R440”, “GL-R430”, and “GL-R420” manufactured by Hitachi Chemical Co., Ltd. are connected in this order. Eluent: Tetrahydrofuran (THF)
Measurement temperature: 23 ° C
Flow rate: 1.75 mL / min
Measurement time: 45 min
Injection volume: 10 μL
Standard polyacrylic acid: “PMAA-32” manufactured by Hitachi Chemical Techno Service Co., Ltd.

  When the CMP polishing liquid contains a water-soluble polymer, the content thereof is preferably 0.001% by mass or more, more preferably in the total mass of the CMP polishing liquid, from the viewpoint of suppressing galvanic corrosion of the cobalt-containing portion. Is 0.005 mass% or more, more preferably 0.01 mass% or more. Further, the content of the water-soluble polymer is preferably 10% by mass or less, more preferably 5.0% by mass or less, in the total mass of the polishing slurry for CMP, from the viewpoint of obtaining a good polishing rate of the cobalt-containing part. Preferably it is 1.0 mass% or less.

<Water>
The CMP polishing liquid contains water. Water is not particularly limited, but pure water can be preferably used. Water may be blended as the remainder, and the content is not particularly limited.

<PH of polishing liquid for CMP>
The pH of the polishing liquid for CMP is 4.0 or less. When pH is 4.0 or less, it is excellent in the polishing rate of a cobalt containing part and a metal containing part. Preferably it is 3.8 or less, More preferably, it is 3.6 or less, More preferably, it is 3.5 or less. Further, the pH of the polishing slurry for CMP is preferably 2.0 or more from the viewpoint of suppressing galvanic corrosion of the cobalt-containing part and the metal-containing part, and from the viewpoint of eliminating difficulty in handling due to strong acidity. 5 or more are more preferable, and 2.8 or more are still more preferable.

  The pH can be adjusted by adding the acid component. It can also be adjusted by adding alkali components such as ammonia, sodium hydroxide, tetramethylammonium hydroxide (TMAH).

  The pH of the CMP polishing liquid can be measured with a pH meter (for example, “Model F-51” manufactured by Horiba, Ltd.). Three-point calibration was performed using a standard buffer (phthalate pH buffer solution pH: 4.01, neutral phosphate pH buffer solution pH: 6.86, borate pH buffer solution pH: 9.18). After that, the electrode is put in a polishing slurry for CMP, and the value after 3 minutes has elapsed and stabilized is measured. At this time, the temperature of the standard buffer solution and the polishing solution for CMP are both 25 ° C.

  The CMP polishing liquid can be applied, for example, to the formation of a wiring pattern in a semiconductor device. Examples of the metal-containing part include a conductive substance part described later. Further, the surface to be polished may include an insulating material portion described later. The materials constituting the cobalt-containing part and the metal-containing part will be described later.

<Polishing method>
The polishing method according to the present embodiment uses at least one of the cobalt-containing portions of the surface to be polished having at least a cobalt-containing portion and a metal-containing portion containing a metal other than cobalt, using the CMP polishing liquid of the above-described embodiment. This is a polishing method in which a portion is polished and removed. Preferably, it is a polishing method for polishing and removing an excess portion of the cobalt-containing portion with respect to the substrate having the cobalt-containing portion and the metal-containing portion formed on at least one surface. More specifically, the substrate is polished while supplying the polishing slurry for CMP according to the above embodiment between the surface of the substrate on which the cobalt-containing portion and the metal-containing portion are formed and the polishing pad on the polishing surface plate. In this polishing method, at least a part of the cobalt-containing portion is polished and removed by relatively moving the substrate and the polishing platen while being pressed.

  The polishing method according to this embodiment can be applied to a series of steps for forming a wiring layer in a semiconductor device. In this case, the polishing method according to the present embodiment includes, for example, an insulating material portion having a concave portion and a convex portion on a surface, a barrier metal portion that covers the insulating material portion along the concave portion and the convex portion, and the concave portion. A conductive material portion that fills and coats the barrier metal portion, the barrier metal portion has a cobalt-containing portion, and the conductive material portion has a metal-containing portion containing a metal other than cobalt. A first polishing step for polishing the conductive material portion to expose the barrier metal portion on the convex portion, and the barrier metal portion exposed in the first polishing step. And a second polishing step for polishing and removing with the CMP polishing liquid in the form. Hereinafter, an example of the polishing method will be described with reference to FIGS. However, the use of the polishing method is not limited to the following steps.

  The substrate shown in FIG. 1 has a cobalt-containing portion 2a as a barrier metal portion and a metal-containing portion 3a as a conductive material portion. As shown in FIG. 1A, a substrate 10 before polishing is formed on a silicon substrate (not shown) along an insulating material part 1 having a predetermined pattern of concave parts and irregularities on the surface of the insulating material part 1. And a cobalt-containing part 2a that covers the insulating material part 1 and a metal-containing part 3a formed on the cobalt-containing part 2a.

  The substrate shown in FIG. 2 has a cobalt-containing portion 2a and a barrier metal portion 2b as the barrier metal portion 2, and a metal-containing portion 3a as the conductive material portion. As shown in FIG. 2A, the substrate 110 before polishing is formed on a silicon substrate (not shown) along an insulating material portion 1 having a predetermined pattern of concave portions and irregularities on the surface of the insulating material portion 1. The barrier metal portion 2b covering the insulating material portion, the cobalt-containing portion 2a covering the barrier metal portion 2b, and the metal-containing portion 3a formed on the cobalt-containing portion 2a.

  Examples of the material forming the insulating material portion 1 include a silicon-based insulator and an organic polymer-based insulator. Silicon-based insulators include silica-based insulators such as organosilicate glass, silicon oxynitride, silsesquioxane hydride obtained from silicon dioxide, fluorosilicate glass, trimethylsilane, and dimethoxydimethylsilane; silicon carbide; A silicon nitride may be used. Examples of the organic polymer insulator include wholly aromatic low dielectric constant insulators. Among these, silicon dioxide is particularly preferable.

  The insulating material portion 1 is formed by, for example, a CVD (chemical vapor deposition) method, a spin coating method, a dip coating method, a spray method, or the like. Specific examples of the insulating material portion 1 include an interlayer insulating film in an LSI manufacturing process, particularly a multilayer wiring forming process.

  The barrier metal portion is formed to prevent the conductive material from diffusing into the insulating material portion 1 and to improve the adhesion between the insulating material portion 1 and the conductive material portion. Examples of the material used for forming the cobalt-containing portion 2a include cobalt compounds such as cobalt, a cobalt alloy, a cobalt oxide, and a cobalt alloy oxide. Examples of the barrier metal used for forming the barrier metal portion 2b include tantalum compounds such as tantalum, tantalum nitride, and tantalum alloys, titanium compounds such as titanium, titanium nitride, and titanium alloys, tungsten compounds such as tungsten, tungsten nitride, and tungsten alloys. Examples include ruthenium compounds such as ruthenium, ruthenium nitride, and ruthenium alloys. The barrier metal part 2b may be, for example, a single layer structure made of one of these or a laminated structure made of two or more kinds. That is, the barrier metal part 2b has at least one selected from the group consisting of a tantalum-containing part, a titanium-containing part, a tungsten-containing part, and a ruthenium-containing part. The barrier metal part is formed by, for example, vapor deposition, CVD (chemical vapor deposition), sputtering, or the like.

  The metal-containing portion 3a as the conductive material portion is mainly composed of copper such as copper, copper alloy, copper oxide, copper alloy oxide or the like, or tungsten such as tungsten or tungsten alloy. Precious metals such as metal, silver and gold can be used. Among these, metals having copper as a main component, such as copper, copper alloys, copper oxides, and copper alloy oxides, are preferable. “A metal mainly composed of copper” refers to a metal having the largest copper content (mass). The metal containing part 3a is formed by, for example, a known sputtering method, plating method or the like.

  The insulating material portion 1 has a thickness of about 0.01 to 2.0 μm, the cobalt-containing portion 2a has a thickness of about 0.01 to 2.5 μm, and the barrier metal portion 2b has a thickness of about 0.01 to 2.5 μm. The thickness of the metal-containing part 3a is preferably about 0.01 to 2.5 μm.

  In the first polishing step, from the state shown in FIG. 1 (a) to the state shown in FIG. 1 (b), or from the state shown in FIG. 2 (a) to the state shown in FIG. 2 (b). The metal-containing part 3a, that is, the conductive substance part is polished. In the first polishing step, the conductive material portion on the surface of the substrate 10 or 110 before polishing, for example, a polishing slurry for CMP for a conductive material having a sufficiently high polishing rate ratio of the conductive material portion / cobalt-containing portion 2a. And polishing by CMP. Thereby, the board | substrate 20 or 120 which has the conductor pattern (namely, wiring pattern) by which the electroconductive substance part on the convex part was removed, the cobalt containing part 2a was exposed on the surface, and the electroconductive substance was left in the recessed part is obtained. . As the polishing slurry for CMP for a conductive material having a sufficiently high polishing rate ratio of the conductive material portion / cobalt-containing portion 2a, for example, the polishing slurry for CMP described in Japanese Patent No. 3337464 can be used. In the first polishing step, a part of the cobalt-containing portion 2a on the convex portion may be polished together with the conductive substance portion.

  In the second polishing step, the cobalt-containing portion 2a exposed by the first polishing step from the state shown in FIG. 1B to the state shown in FIG. Use and polish to remove excess cobalt-containing part.

  Further, as shown in FIG. 2, when the barrier metal part 2 has a cobalt-containing part 2a and a barrier metal part 2b, the state shown in FIG. 2 (b) is changed from the state shown in FIG. 2 (b). The cobalt-containing part 2a and the barrier metal part 2b are polished until the excess cobalt-containing part and the extra barrier metal part 2b are removed. At this time, the cobalt-containing portion 2a is polished with the CMP polishing liquid of the above-described embodiment. When the barrier metal portion 2b is exposed, the polishing is terminated, and the barrier metal portion 2b is separately polished with the CMP polishing liquid for polishing the barrier metal portion 2b. The metal part 2b may be polished. Further, as a series of steps, the cobalt-containing portion 2a and the barrier metal portion 2b may be polished with the CMP polishing liquid of the embodiment.

  The insulating material part 1 under the protruding barrier metal part (cobalt-containing part 2a or cobalt-containing part 2a and barrier metal part 2b) is completely exposed, leaving a conductive substance part that becomes a wiring pattern in the concave part, The polishing is finished when the substrate 30 or 130 having a desired pattern in which the cross section of the barrier metal part is exposed at the boundary between the convex part and the concave part is obtained. Furthermore, the conductive material portion embedded in the recess may be polished together with the barrier metal portion.

  In the second polishing step, a polishing liquid for CMP is supplied between the polishing pad and the substrate while the substrate 20 or 120 is pressed on the polishing pad of the polishing surface plate with the surface to be polished facing the polishing pad. However, the surface to be polished is polished by relatively moving the polishing surface plate and the substrate 20 or 120.

  As an apparatus used for polishing, a general polishing apparatus having a holder for holding a substrate to be polished and a polishing platen connected to a motor capable of changing the number of rotations and attached with a polishing pad can be used. As the polishing pad, a general nonwoven fabric, foamed polyurethane, porous fluororesin, or the like can be used, and there is no particular limitation.

The polishing conditions are not particularly limited, but the rotation speed of the polishing surface plate is preferably a low rotation speed of 200 min ⁻¹ or less so that the substrate does not pop out. The pressure for pressing the substrate against the polishing pad is preferably 1 to 100 kPa, and more preferably 5 to 50 kPa in order to satisfy the in-surface uniformity of the polishing rate and the flatness of the pattern.

  During polishing, the CMP polishing liquid of the above embodiment is continuously supplied by a pump or the like between the polishing pad and the surface to be polished. Although the supply amount is not limited, it is preferable that the surface of the polishing pad is always covered with a CMP polishing liquid. The substrate after polishing is preferably washed in running water and then dried after removing water droplets adhering to the substrate using spin drying or the like.

  In order to perform CMP with the surface state of the polishing pad always the same, it is preferable to perform a polishing pad conditioning step before polishing. For example, the polishing pad is conditioned with a liquid containing at least water using a dresser with diamond particles. Subsequently, it is preferable to carry out the polishing method according to this embodiment and further add a substrate cleaning step.

  On the wiring pattern thus formed, a second layer insulating material part, a barrier metal part, and a conductive substance part are further formed, and then polished to obtain a smooth surface over the entire surface of the semiconductor substrate. And By repeating this step a predetermined number, a semiconductor device having a desired number of wiring layers can be manufactured.

  The polishing slurry for CMP of the present invention can be used not only for polishing a semiconductor substrate as described above, but also for polishing a substrate such as a magnetic head.

  EXAMPLES Hereinafter, the present invention will be described more specifically with reference to examples. However, the present invention is not limited to these examples without departing from the technical idea of the present invention. For example, the type and ratio of the CMP polishing liquid material may be other than the type and ratio described in this example, and the composition and structure of the polishing target may be other than those described in this example. Absent.

<Preparation method of polishing liquid for CMP>
Using the components shown in Table 1, a CMP polishing liquid was prepared by the following method.
(Examples 1-6 and Comparative Examples 1-2)
Metal anticorrosive of the type shown in Table 1, 3-methoxy-3-methyl-1-butanol as an organic solvent, polyacrylic acid ammonium salt (weight average molecular weight 8,000) as a water-soluble polymer, and abrasive grains (polishing) Colloidal silica (average secondary particle size 60 nm) was put in a container as particles), and ultrapure water was further poured and mixed by stirring to dissolve all components. After adding hydrogen peroxide water (30% by mass aqueous solution) as an oxidizing agent, ultrapure water was added to make the whole 100 parts by mass, and a polishing liquid for CMP was obtained.

  The content of each component is as shown in Table 1. The content of the abrasive grains is shown as mass% of “silica particles”, and the content of the oxidizing agent is shown as mass% of “hydrogen peroxide”. The average particle diameter (average secondary particle diameter) of colloidal silica and the weight average molecular weight of polyacrylic acid ammonium salt were measured according to the above-mentioned method.

<Measurement method of pH>
The pH of the CMP polishing liquid was measured according to the following.
Measurement temperature: 25 ° C
Measuring instrument: “PHL-40” manufactured by Electrochemical Instruments Co., Ltd.
Measurement method: standard buffer (phthalate pH buffer solution pH: 4.01 (25 ° C.), neutral phosphate pH buffer solution pH: 6.86 (25 ° C.), borate pH buffer solution pH: 9 .18 (25 ° C.) was used to calibrate at three points, and then the electrode was put into a CMP polishing liquid, and the value after 3 minutes had elapsed and stabilized was measured, and the results are shown in Table 1.

<Etching amount evaluation for cobalt>
A blanket substrate (a) in which a cobalt layer having a thickness of 200 nm was formed on a 12-inch silicon substrate was prepared. The blanket substrate (a) was cut into 20 mm square chips to prepare evaluation chips (b).

  Each of the evaluation chips (b) was placed in a beaker containing 100 g of each of the abrasives (CMP polishing liquid), and immersed in a constant temperature bath at 60 ° C. for 1 minute. The evaluation chip (b) after immersion was taken out and thoroughly washed with pure water, and then nitrogen gas was blown to dry the water on the chip. The resistance of the evaluation chip (b) after drying was measured with a resistivity meter and converted into the film thickness of the cobalt layer after immersion by the following formula (1).

A calibration curve was obtained from information on resistance values corresponding to the respective film thicknesses of the blanket substrate (a), and the film thickness of cobalt was determined from the following formula (1).

Film thickness [nm] of cobalt layer after immersion
= 104.5 × (resistance value [mΩ] / 1000 of evaluation chip (b)) − ^0.893
... (1)

And the etching rate of the cobalt layer was calculated | required from following formula (2) from the film thickness of the obtained cobalt layer after immersion, and the thickness of the cobalt layer before immersion.

Etching rate of cobalt layer (Co-ER) [nm / min]
= (Cobalt layer thickness before immersion [nm] -Cobalt layer thickness after immersion [nm]) / 1 minute (2)

  About each abrasive | polishing agent obtained above, the etching rate with respect to a cobalt layer was calculated | required. The results are shown in Table 1.

<Polishing rate evaluation for cobalt>
Further, the polishing rate (Co-RR) [nm / min] when the blanket substrate (a) was polished under the following conditions using each of the abrasives (CMP polishing liquid) obtained above was determined. . The results are also shown in Table 1.

<Polishing conditions>
Polishing device: Polishing machine for single-sided metal film ("Reflexion LK" manufactured by Applied Materials)
Polishing pad: Polishing pad made of foamed polyurethane resin Surface plate rotation speed: 93 min ⁻¹
Polishing head rotation speed: 87 min ⁻¹
Polishing pressure: 10.3 kPa (1.5 psi)
Supply amount of polishing liquid for CMP: 300 mL / min
Polishing time: 0.5 min

[Cleaning of polished substrate]
After pressing a sponge brush (made of polyvinyl alcohol resin) onto the surface to be polished of the substrate polished above, the substrate to be polished and the sponge brush were rotated while supplying distilled water to the substrate to be cleaned, and washed for 1 min. . Next, after removing the sponge brush, distilled water was supplied to the surface to be polished of the substrate to be polished for 1 minute. Finally, the substrate to be polished was rotated at a high speed to blow off distilled water, and the substrate to be polished was dried.

As is apparent from Table 1, when the metal anticorrosive of Comparative Example 1 is not used, the cobalt polishing rate is high, but the etching rate is also high. Further, when an inorganic acid salt is included as in Comparative Example 2, both the cobalt polishing rate and the etching rate are increased.
On the other hand, in Examples 1-6, by including two types of specific metal anticorrosive agents, the etching rate of cobalt is remarkably suppressed even at 60 ° C., and the cobalt layer can be polished at an appropriate polishing rate. all right.

  According to the CMP polishing liquid and the polishing method according to the embodiment of the present invention, cobalt etching can be suppressed while maintaining the polishing rate of the cobalt-containing portion as compared with the case where a conventional CMP polishing liquid is used.

DESCRIPTION OF SYMBOLS 1 Insulation material part 2 Barrier metal part 2a Cobalt containing part 2b Barrier metal part 3 Conductive substance part 3a Metal containing part 10,110,210 containing metals other than cobalt First polishing | polishing board | substrate 20,120,220 1st grinding | polishing Substrate 30, 130, 230 after the process Substrate after the second polishing process

Claims (10)

  A polishing slurry for CMP used for polishing a surface to be polished having at least a cobalt-containing part and a metal-containing part containing a metal other than cobalt, which contains two types of metal anticorrosives, abrasive particles, and water. A polishing slurry for CMP having a pH of 4.0 or less and the two types of metal anticorrosives being both azoles (excluding inorganic acid salts).   The polishing slurry for CMP according to claim 1, further comprising a water-soluble polymer.   The CMP particle according to claim 1 or 2, wherein the abrasive particles include at least one selected from the group consisting of silica particles, alumina particles, ceria particles, titania particles, zirconia particles, germania particles, and modified products thereof. Polishing fluid.   The polishing liquid for CMP as described in any one of Claims 1-3 which further contains a metal oxidizing agent.   The polishing slurry for CMP according to any one of claims 1 to 4, further comprising an organic solvent.   Using the polishing slurry for CMP according to any one of claims 1 to 5, at least the cobalt-containing portion of the surface to be polished having at least a cobalt-containing portion and a metal-containing portion containing a metal other than cobalt. A polishing method in which a part is removed by polishing. Insulating material portion having concave and convex portions on the surface, barrier metal portion covering said insulating material portion along said concave and convex portions, and conductive material portion filling said concave portion and covering said barrier metal portion Preparing a substrate having a metal-containing portion in which the barrier metal portion has a cobalt-containing portion, and the conductive material portion contains a metal other than cobalt,
The first polishing step for polishing the conductive material portion to expose the barrier metal portion on the convex portion, and the barrier metal portion exposed in the first polishing step according to any one of claims 1 to 6. A polishing method comprising a second polishing step of polishing and removing with the CMP polishing liquid according to claim 1.   The polishing method according to claim 7, wherein the insulating material portion contains a silicon-based insulator or an organic polymer-based insulator.   The polishing method according to claim 7 or 8, wherein the conductive substance portion contains copper as a main component.   The barrier metal part according to any one of claims 7 to 9, wherein the barrier metal part has a cobalt-containing part and at least one selected from the group consisting of a tantalum-containing part, a titanium-containing part, a tungsten-containing part, and a ruthenium-containing part. The polishing method described.

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